If the 3090 is so powerful why would anyone need SLI??? And why have Nvidia stopped SLI for the lower models? So gimp lower cards with less RAM, end SLI for all but the flagship card and charge the Earth for the privilege.
I'm waiting for Hawaii and Tahiti's kick ass grandchild before spending anything. The power budget and ludicrously big cooler for Ampere suggest Jensen is shook.
Plenty renderers take advantage of multi GPUs. Octane render and redshift being a few. Time is money. If you can make that money back in a few projects then it makes sense.